Today's planar digital image sensors simply inherit their form factor from the substrates and semiconductor processes used in their volume manufacture. But more and more research groups are pursuing the benefits of curved hemispherical sensors, mimicking the optimized optics of biological eye systems.

The sensor array consists of hexagon-shaped
photodiodes, with a metal connector waving from
one cell to the next. Scale bar in the microscope
image is 50μm.

In their implementation, the researchers packed 281 hexagonally-shaped photodetectors (each 113 μm in diagonal) in hemispherical arrays of different radii, 2.27mm and 7.20mm, only observing a performance degradation when the photodetector was conformed to a curvature radius of 1.5mm. But they note that if made thinner (down to 20nm), a silicon nanomembrane photodetector could easily wrap around a single mode fibre (125μm in diameter).

Close up of hexagonally-shaped pixels from the
origami sensor draped over a dome shape, with
perfectly jointing seams. Yei Hwan Jung and Kan Zhang.

The hemispherical FPA was assembled into a simple camera system featuring a plano-convex lens (10mm diameter and 10mm focal length) while the convex version was evaluated as a compound eye mimicking camera (a photoresist microlens placed on top of each detecting unit during fabrication to maximize light intake).

The paper highlights the simplicity of the origami-shaping process and how easily the pixel density could be scaled up. The researchers hope that further optical optimizations of their compound electronic eye system (such as adding layers to mimic the pigment cells and crystalline cones) could yield truly panoramic colour vision.